Soyuz 7K-OK
The Soyuz 7K-OK vehicles carried a crew of up to three without spacesuits. The craft can be distinguished from those following by their bent solar panels and their use of the Igla automatic docking navigation system, which required special radar antennas.
The 7K-OK was primarily intended as a variant of the 7K-LOK (the lunar mission Soyuz) for Earth orbital testing. Mostly the same vehicle, it lacked the larger antenna needed to communicate at lunar distance. The early Soyuz models also sported an external toridal fuel tank surrounding the engines and meant to store extra propellant for lunar flights, but it was left empty on Soyuz 1-9. After the spacecraft was converted to a space station ferry, the tank was removed.
Soyuz 7K-OK spacecraft had an docking mechanism of the original Soyuz "probe and drogue" type to dock to other spacecraft, in order to gather engineering data as an preparation for the Soviet space station program. There were two variants of Soyuz 7K-OK: Soyuz 7K-OK(A) featuring an active "probe" docking port, and Soyuz 7K-OK(P) featuring an passive "drogue" docking target. For unknown reasons, both the 7K-OK and 7K-LOK did not have docking mechanisms that opened or allowed internal transfer (this did not arrive until the 7K-OKS), thus cosmonauts had to spacewalk for this. The procedure was done successfully on the joint Soyuz 4 and Soyuz 5 missions, where Aleksei Yeliseyev and Yevgeny Khrunov transferred from their Soyuz 5 to the Soyuz 4 craft.
The first unmanned test of this version was Cosmos-133, launched on Nov. 28, 1966.
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